>> INSERT INTO mytable(...) VALUES(...);
>> SET @Id=LAST_INSERT_ID();
>> UPDATE mytable SET col1=MOD(@Id, 30) WHERE id=@Id;
>> -- More rows:
>> INSERT INTO mytable(...) VALUES(@Id, ...);
>>
>> This should be done in one connection session, otherwise the variable
>> @Id is cleared.
>
> Yes, but it's less efficient than when updating multiple rows. Each
> entry has an INSERT, a SET and an UPDATE. This requires three
> statements to be parsed and executed for each insert - much slower,
> unless you have a very slow database connection.
>
> My way has one INSERT per row, on get last insert id and a single
> UPDATE. Parsing/execution will be much faster.

The last INSERT can have more than one row and could even be delayed, I
think. If the data to insert is not too complicated, you could even
write a stored procedure for the above queries. I think the above
queries are not more load than the "external" ID handling, but it can
take some load of the webserver or the data traffic.

Best regards
--
Willem Bogaerts

Application smith
Kratz B.V.
http://www.kratz.nl/